Usually, the primary cooling circuit is in fluidic communication with the outside of the frame of the motor so as to allow cooling of the stator by having ambient air circulate in the primary cooling circuit. Generally, the secondary circuit is, as for it not in fluidic communication with the outside of the frame of the electric motor in order to avoid that dust or other materials jam or foul the mobile portion of the motor. Consequently, the secondary circuit is connected to a cooling device extending outside the motor, so as to allow a heat exchange between the fluid gas circulating in a closed circuit in the secondary circuit and outdoor air through the wall of the cooling device.
Such an electric motor is for example described in document U.S. Pat. No. 6,891,290.
However, the architecture of such an electric motor implies that the secondary cooling circuit of the rotor crosses the primary cooling circuit of the stator. This crossing of both circuits hampers the cooling efficiency of the primary cooling circuit of the stator since the total volume of the primary cooling circuit has to be limited in order to let through the secondary cooling circuit.